There are at least two important problems related to the safety and health of the vehicle occupants. One of these problems, the problem of vehicle occupant safety, has now become a nation-wide problem for the USA and other countries. Most American cars are equipped with a safety air bag system such as Supplemental Restraint Systems (SRS).
To improve performance of various safety devices such as SRS, operations of the safety devices have been controlled in accordance with the weight of a passenger sitting on a vehicle seat.
In some safety air bag SRS systems, a vehicle Passenger Classification System is described that uses the differences in weight between adults and small children, and a control unit identifies vehicle occupants using input values from weight sensors installed between the leg frames fixed on the floor and moving rails of a car seat.
In other SRS systems, the sensors for measuring the weight of a seated passenger are disposed between moving rails of a car seat and a frame of the vehicle seat.
In the U.S. Pat. No. 7,991,530 “System and method for classifying vehicle occupant” by Cho et al., a vehicle Occupant Classification System is described that uses the differences in weight between adults and small children, and a control unit identifies vehicle occupants using input values from weight sensors installed between the leg frames and moving rails of a seat, and results of sensing are transmitted to an Airbag Control Unit (ACU). However, the above-described system for classifying a vehicle occupant has problems in that it is difficult to install sensors in a seat and the complexity of work increases because respective components of the system have to be individually installed in a seat.
Because a load sensor is typically disposed in a narrow space between the vehicle floor and the vehicle seat, it is difficult to do maintenance on the load sensor. Further, dismounting the entire vehicle seat for easier maintenance is inefficient.
In another type of safety air bag the SRS system described in the U.S. Pat. No. 9,140,588, “Vehicle seat comprising load sensor and side frame with upper-side protruding section and lower-side protruding section” by Endo et al., a vehicle passenger's weight measurement device for a vehicle seat comprises a movable rail on a fixed rail, a load sensor which is mounted on an upper surface of the movable rail, a cushion frame which is mounted on the load sensor, and a pan frame, wherein the efficiency of the load sensor maintenance is improved. However, there is a dimension error or an assembling position error when the passenger's weight measurement device is assembled, when the vehicle seat is fixed to the passenger's weight measurement device or when the passenger's weight measurement device is fixed to the vehicle floor, or the like. Accordingly, it has been difficult to assemble the passenger's weight measurement device.
In this regard, another type of conventional safety air bag system is described in the U.S. Pat. No. 9,156,384, “Vehicle seat comprising load sensor and side frame having a concave part”, by Takayasu et al., to provide a passenger's weight measurement device for a vehicle seat, which is more easily assembled, and to provide an attachment structure for a load sensor. In this invention, a vehicle seat includes a load sensor that is configured to measure a load applied from an occupant and that has an extending rod, a seat cushion frame that includes right and left side frames that extend along a front-rear axis, and a bracket member attaching the load sensor to at least one of the right and left side frames.
As we can see from the inventions described above, the occupant's weight measuring sensor has been moved from the low part of the sliding rails, where it touches the upper part of the lower rails fixed on the vehicle's floor. This is a useful step in improving of the access, maintenance, and life span of the weight sensor relative to the structure of the air bag devices where the weight sensors are installed on the leg frames fixed on the floor.
Despite these improvements, the Passenger Classification System of the air bag SRS systems is still limited because the capacity of the load sensor is fixed and the weight span of the possible vehicle occupants is too wide for accurate weight measurements in different weight categories.